Most people do not live to work, but work to live. They find it galling to hear Westminster insiders with interesting jobs hectoring them about grinding on for longer. George Osborne's call yesterday for a rise in the pension age is likely to be taken that way, even though it embodies a cold logic. That logic first led the Turner commission to recommend the rise which the shadow chancellor now wants to speed up.

Pensions once supported people for two or three years, but now it is more like two to three decades. Mr Osborne sometimes talks about "the fruits of economic growth", and – once recovery arrives – these might have been banked on to cover the costs, were it not for the new cross-party consensus for restoring the link between pensions and earnings. That will give pensioners their fair share of rising prosperity, but will also consume all the available fruits. Extending longevity will therefore entail either new taxes or working for longer. State pension costs are the biggest chunk of the welfare bill, at £63bn a year. Raising the qualifying age by a year might shave 3%-6% from that total, far more than would be got by a full-frontal assault on smaller benefits paid to the poor. In theory, at least, it should also carry a less devastating social cost.

In practice, however, everything depends on the steps taken to protect the vulnerable – detail we heard little about yesterday. Life expectancy has, after all, risen faster in rich communities than in poor ones, as David Cameron pointed out in the days before financial conservatism overshadowed the compassionate strain. Asking dispossessed older people, sometimes with failing health, to scrape by on the weekly £64.30 of jobseeker's allowance is not a tolerable option. It is more objectionable still if coupled with plans to hector claimants into jobs.

The first thing needed is a clear pledge to ensure that pension credit, which is paid to the poorest, will remain available to 65-year-olds. At the same time there is an urgent need to end the continuing scandal of employers shunting staff out simply on grounds of age. Last but not least, there are the implications for women. Their pension age is already rising to match that of men, as is required by European equality laws.

The Tories belatedly recognised yesterday that women would not take kindly to being asked to swallow two age rises at once. But they could not explain how they would target the early increases on men without falling foul of Brussels – instead they responded in Brownian style, by promising a review. Asking us all to work longer is a tough sell. To make it persuasively, the Conservatives must first show they have done their homework.